question related to using join in Expression Rule

Question

Hi All, 
 i have a query related to using join in expression 
 as you can see their is a logic mentioned in below code which is i am using in a database view but now i need to use this logic in expression rule to fetch the data so any one can help me to implement this logic or you can give any example 
 we requird the filter on below case 
 SELECT a.IDeChangeAffectedElements as IDsiteHistory, a.eChangeRequestDetailsID, a.siteid, a.sitename, a.location, a.network, a.elmid, a.elmalias, a.elmaddress, a.createdby, a.createddate, a.modifiedby, a.modifieddate , b.plannedstartdate as startdate, b.plannedenddate as enddate, b.EtimeCode FROM eChangeAffectedElements a WITH(NOLOCK) left join eChangeRequestDetails b WITH(NOLOCK) on a.eChangeRequestDetailsID = b.IDeChangeRequestNumber

Mike Schmitt · Answer

If you're doing traditional (entity-wise) querying in the expression rule, you merely create a DB view that utilizes the joining logic you want, create a Data Store Entity pointing to that view, then query it in your code. 
 If you're using RecordType data (synced records etc), you should be able to do basically the same thing inherently in your data structure by configuring Related Record Data. 
 As Stefan mentioned, "joins" in expression code aren't really a thing. The closest you could come is to query from table A and query from table B with filtering on the values you've already retrieved from A, which could work depending on what your requirements are, but doesn't scale well (it gets pretty costly if your volume of queried data starts to become large at all), and doing the necessary coding requires precise and sometimes confusing intricacy.